dnsdist: Move the console socket instead of copying it

[rgacogne]

Short description

Reported by Coverity as CID 414105. We don't really care about the performance impact but other tools are "helpfully" reporting this kind of missed optimizations, so let's not waste our time.

Checklist

I have:

• read the CONTRIBUTING.md document
• compiled this code
• tested this code
• included documentation (including possible behaviour changes)
• documented the code
• added or modified regression test(s)
• added or modified unit test(s)

[coveralls]

Pull Request Test Coverage Report for Build 7622614387

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.004%) to 57.665%

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Totals
Change from base Build 7622389749:	-0.004%
Covered Lines:	107790
Relevant Lines:	155537

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💛 - Coveralls